The invention relates to armature laminae for a dynamoelectric machine and more particularly to a form of such laminae that is useful in constructing a random wound dynamoelectric machine armature in which a maximum number of turns of an energizing winding are to be positioned within the respective conductor slots of the armature.
It is common practice to form an armature for a random wound dynamoelectric machine by first stacking a selected number of pre-formed, soft iron laminae on a suitable spindle, then placing sets of energizing coils in respective pairs of winding slots formed in the peripheries of the laminae, and finally encapsulating the assembly with a coating of insulating resin. Heretofore, in the manufacture of such armatures the usual practice was to make each of the laminations substantially identical to one another and to form the respective winding-receiving slots in the laminae so that they would be substantially identical to one another. In such prior art armature constructions each of the winding slots typically was provided with a mouth, or winding-receiving opening, that was centered relative to the associated slot.
As energizing coils are successively wound in the slots of such known types of armature constructions, all of the turns in each coil are normally positioned to one side or the other of the armature spindle. This conventional winding procedure causes the turns of the first half of the coils wound on the armature to be positioned primarily within the lower radial halves of the respective winding slots. As the second half of the coils are positioned in the slots, they are also wound so that all of their turns are positioned on a given side of the armature axle. Due to the fact that these later-applied coils must lay over the initially applied coils in the radially extended portions thereof surrounding the armature axle, the respective turns of these later coils are necessarily disposed primarily in the radially outer halves of the respective winding slots.
When the individual turns of the last-applied coils are wound onto the armature, they build up on one side of the slots and over the earlier-applied turns until the mouths of the slots become blocked. Since it is then practically impossible to economically insert additional winding turns into the respective slots, particularly when an automatic winding machine is being utilized, the slots are not completely filled with copper. Specifically, the area of the respective slots located to that side of the centered mouth of each slot opposite the side of the slot on which the windings are initially applied, is not filled with winding turns. Due to this incomplete filling of each of the winding slots, the theoretical design efficiency of the armature is necessarily substantially less than it would be if each of the slots had been completely filled with turns of an energizing winding.
It is generally known in the prior art that conductor bars of induction motors can be partially secured in operating position within punched slots of rotor laminations by forming small projections on one side of such slots adjacent the top edge thereof. An example of the use of such projections to help hold induction motor conductor bars in position, against centrifugal forces produced by rotation of the rotor, is shown in U.S. Pat. No. 3,375,385, which issued on Mar. 26, 1968.